Low cost portable computing devices such as handheld or palm-sized computers are widely available. Such devices can support local communication between nearby computers, or more generally can support wireless network or internetwork communications. Users equipped with suitable portable computers can, for example, exchange e-mail, browse the web, utilize mapping software, control nearby computer peripherals (e.g. printers), or receive information from local devices (e.g. job status of a printer). As will be appreciated, flexibility and utility of various applications can be enhanced if the precise spatial location of the portable computing device is known. Knowing the location of the portable computing device (with a precision of several meters or so) permits construction of user specific maps, transfer of location information to others, and receipt of location information for nearby computational or real world resources (e.g. answering such questions as "where is the nearest printer" or "where is the nearest coffee shop"). For this reason, having easily determinable and reliable position information is a useful feature.
However, spatial localization with low cost devices can be difficult. Devices incorporating GPS receivers often do not work indoors because of poor radio reception and can require a substantial amount of time to determine position with a required accuracy. In many areas, there may not be any differential GPS availability to gain the necessary meter level precision for greatest utility. Other wireless schemes for localizing spatial position are generally not sufficiently precise (e.g. digital cellular telephone service areas with 1000 meter errors), or too expensive (inertial navigation systems).
According to the present invention, one solution for determining spatial location is based on low cost infrared equipped devices and infrared beacons. Outdoor situated infrared beacons that broadcast a unique identification number can be precisely located outdoors using differential GPS in a one-time procedure. Indoor situated infrared beacons that broadcast a unique identification number can be precisely located indoors using architectural plans in combination with accurate survey maps or external GPS of the building. Relative location is even of infrared beacons is even simpler. For example, each room in an office building can be equipped with a unique identification number, and geographic references are made with respect to room numbers rather than x,y,z absolute position. In any case, whether absolute or relative positioning is used, the location information is linked to the unique identification number available over the Internet or through local database spatial localization services. In operation, a portable computing devices equipped with an infrared receiver can receive the data signal from the infrared beacon, enabling high precision determination of physical location both indoors or outdoors. In certain embodiments, a GPS receiver integrated with a portable computer can be used to roughly determine location, with more precise positioning being handled by reference to infrared beacons.
In preferred embodiments, an infrared beacon is integrated into convention incandescent, fluorescent, or high intensity discharge lamps (e.g. metal halide, high or low pressure sodium lamps) suitable for indoor or outdoor usage. The infrared beacon includes a light source removably attachable to lighting fixtures that supply electrical power at a determined voltage and a voltage converter electrically and physically connected to the light source to provide a reduced supplied voltage. For indoor usage, electrical power is typically supplied at 110 Volts AC, and is converted to less than 5 or 6 volts DC by the voltage converter. Outdoor power supplies are often higher (220 Volts AC or greater), and power supplied by the voltage converter may also be slightly higher.
In operation, the infrared beacon, powered by the voltage converter, continuously, intermittently, or in response to an interrogatory signal, broadcasts a data signal. This data signal can be predetermined, and is typically a series of infrared pulses adhering to IrDA standards. In certain embodiments, a microcontroller and oscillator are attached to trigger the microcontroller to initiate the electrical pulse train resulting in broadcast of the data signal. Alternatively, a special trigger circuit responsive to infrared, optical, physical (e.g. pushbutton or switch), or radio frequency input can be used, alone or in combination with a microcontroller or oscillator circuit, to initiate broadcast of the data signal.
Additional functions, objects, advantages, and features of the present invention will become apparent from consideration of the following description and drawings of preferred embodiments.